Stabilization of fats for soap



, from low-grade sources, e. g. propane fractiona- Pat'ent'ed `lune l, 1954 UNITED STATES PATENT OFFICE STABILIZATION OF FATS FOR SOAP Howard C. Black', Chicago, and JohnH. Johnson, Park Forest, Ill., assignors to Swift & Company, Chicago, Ill., a corporation of Illinois Application September 14, 1951, Serial No. 246,618

18 Claims. (Cl. 260--398.5)

1 2l The present invention relates in general to the in the art from the following detailed description stabilization of soap or soap products and', more of the invention. l particularly, to a'method for the preparation of ln accordance with the present` invention, it is stabilized soaps from low-grade fatty materials. contemplated that any fatty materials obtained Light-colored soap or soap products, designed 5 from low-grade fatsources which are suitable for to be placed on the competitive consumer market, soap making Abut have heretofore been considered have heretofore been made from top-grade prime impractical for use in high-grade soap or soap fatty materials due to the tendency of soaps made products due to the dark color and the instability from low-grade fatty materials to become rancid of the resulting soaps, may be used. These lowand discolored upon relatively short exposure to l grade fatty materials are preferably of animal light and air. Attempts have been made to overorigin, such as greases and tallows, including come this instability of soaps from low-grade fat those commonly known in the trade as yellow sources by adding various soap antioxidants grease, brown grease, garbage grease, No. l talthereto. These prior art attempts have failed to low', No. 2 .tallow, and Diamond S tallow. The

produce products which could compete favorably, I commercial specifications of the fats sold under from a rancidity or color-reversion standpoint, the aforesaid trade names are as follows:

Yellow Brown Garbage No.1 No.2 Diamond Grease Grease Grease Tallcw Tallow VSTallow F. F. v.A.=l3`ree fatty acid.

M.l I. U.=Moisture, insoluble and unsaponiiiable.

F. A. C.=Fatty Analysis Committee ot American Oil Chemists Society.

with soaps made from better-grade fatty mate- Decolorization of these` materials greatly imrials. Recent improvements in methods of improves their appearance, making them comparable in this respect to higher-grade fats. However, when they are used in the manufaction and the like, have made available great ture of soap, the soap, while initially lightquantities of such materials but, due to their colored, will be found to become rancid and inherent properties and instability, they have not dark upon aging. The addtiOIl 0f. S'Oap antlbeen utilized to any appreciable extent in the OXdaIltS t0 sapsmad'e frOm these 10W-grade desoap-making industry `for the manufacture 0f colorlzed fatty materials or the addition of fat proving the color and quality of fatty materials light-colored, highg1ade soaps, antioxidants to the decolorized material prior to It is, therefore, an object of the present invenits use in the Soap-making process fails t0 impart tion to provide a method for producing a satis- Stability 60 the SODS fOrmed.

factory, stable soap from lowgrade fatty mate- 40 lf the 10W-grade fatty material, dGCOlOTZed, as

ria1s for example, by contact with a liquefied, normally It is a further object of the invention to progaSGOU'S' hydrocarbon, i'S treated With a fat anti'- vide a method for producing a soap from 10W- oxidant immediate-ly after decolorizing, and then grade fatty materials which does not become after SaDOIl'CGOII O' the fat, S additionally rancid even after long exposure to accelerated treated With a S'Oap antOXdallt, the resultant' aging conditions. y soap is equivalent to that made from the best Another object of the present invention is to grades 0f fat- It has been found that a Synerprovide an antioxidant composition which has gstlc elle@ isbtaned by adding the fait ami a synergistic effect in retard'ing rancidity and OXdanlS t0 the 10W-grade fatty material, decolor reversion in. soaps made from low-grade colorized as hereinafter disclosed, and after the fatty materials. treated Afatty material has. been saponiied, add- Additional objects, if not specifically set forth ing the soapv` antioxidant to the soap so proherein, will be readily apparent to one skilled duced. The resultant product possesses much greater stability with respect to the development of rancidity and discoloration than does soap prepared from fat which has been treated With a fat antioxidant alone or from a fat which is untreated and a soap antioxidant alone is used. The fat antioxidant is added to the decolorized material as soon after decolorizing as possible, preferably before the decolorized material has been exposed to air. The usual methods of saponiication are then carried out and the soap antioxidant is then added to the soap at any time after saponication has taken place.

The fat antioxidants are preferably a phenolic type. As applied to the manufacture of soap by the kettle-boiling process, the so-called hindered phenolic compounds are preferred. By this term is meant phenols which have large substituents on the aromatic ring, particularly in one or both of the ortho positions. An important characteristic of these antioxidants is that they are relatively insoluble in dilute (2-3 per cent) sodium hydroxide solutions. In general, the more and the larger the substitutents around the phenolic group, the less soluble the compound is in caustic solutions. Examples of such compounds are 2,5, di-tertiary-butyl hydroquinone, para-tertiary-butyl phenol, 2,6, di-

ene-diamine, cyanoguanidine, and the mercaptobenzothiazole salt of phenylbiguanide. The synergistic eiect is most pronounced when the biguanide soap antioxidants are used, such as 5 ortho-biphenyl or ortho-tolyl biguanide.

The amounts of fat and soap antioxidants may vary, but usually come within the range of about 0.05 to 1 per cent. A preferred amount of either antioxidant is about 0.1 per cent. A convenient l method of adding the soap antioxidant is in combination with dry sodium silicate, for example 0.1 per cent antioxidant and 0.6 per cent sodium silicate.

Soap made by the kettle-boiling process in l accordance with the present invention was tested under accelerated aging at 100 per cent humidity and at room temperature (Table I) or 50 C. (Table II), and the rancidity increase noted organoleptically by a panel of three soap experts and also by measurement of the accelerated increase in peroxide value, e. g. .after uniform exposure to controlled ultraviolet light for one hour. As a general rule, a soap with a lower degree of odor stability than another will show a larger peroxide increase lupon aging. The fat samples in the following tables were decolorized by treatment with propane as will be more fully described l tertiary-butyl meta-cresol, 2,6, di-tertiary-butyl below.

Table I Without Soap Antioxidant With Soap Antioxidant Type oi Fat Used in Soap Odor P d Odor eroxi e Peroxide Increase Days to Dsfo Increase Da to Dto (Good) (7) (Y) (-1-) (GOOG) (l) Decolorized tallow plus An..- l5 7 39 21.9 42 48 6 0 55 20. 2 69 69 g2) Decolorized tallow plus AL--- l1 13 37 25. l 4l 44 l2 1 48 23. 6 55 69 3g Decolorized tallow plus M 2l 16 24 30. 3 20 29 8 l 52 28. l 69 )69 (4 Decolorized tallow (N o phenolic antioxidant) ll 39 l1 36.6 4 13 23 0 38 33.8 17 69 (5) Bleached prime tallow (No antioxidant) 13 30 18 29. 6 3 l5 (l 0 61 24. 3 69 69 In the above table:

AF2, 5, mercury-butyl hydroqu'mene `(0.1% by weight added).

(-1-) :This column represents number of times sample considered to be rancid during the (iQ-day aging period. (?)=This column represents number of times sample considered to be a borderline case of rancidity during the (S9-day aging period. **=These columns give the approximate number of days before the sample appeared to be denitely rancid or a borderline case p-phenyl phenol, 2,4,6, tri-tertiary-butyl phenol and the like. The fat antioxidant used in connection With the kettle process should be relatively insoluble in dilute caustic to prevent leaching out by the lye during the soap boiling operation.

In soap-making processes other than kettle boiling the caustic solubility of the phenolic antioxidant becomes less important since all of the phenol added initially remains in the soap formed so as to give the desired synergistic eifect With the soap antioxidant. Therefore, when the present invention is applied to the cold-made or continuous soap-making processes, any of the known phenolic fat antioxidants including those relatively soluble in dilute caustic solutions, such as p-tertiary-butyl catechol, propyl gallate, pyrogallol, ortho-butyl para-hydroxy anisole, or

the like may be used.

The soap antioxidants which may be used in the present invention may be any amino-type antioxidant effective in retarding loss of color and rancidity of the soap, such as ortho-biphenyl or ortho-tolyl biguanide, diphenyl-para-phenylture and diiiused room light.

stability of the various samples.

The tests indicated in Table I were carried out by placing the various soap samples in stender dishes at 100 per cent humidity, room tempera- The samples were tested daily and the observations of the panel recorded as indicated in the above table. The test, being organoleptic, was not quantitatively determinative, but as indicated, the number of 60 times the odors of the samples Were questionably guanide) it will be seen from the above table that the odor of such soap was considered neither rancid nor questionably rancid at any time during the 69-day test, and also that the peroxide increase was small (24.3). .A soap made from a low-grade, propane-decolorized tallow (4) will @meint-122 5 6 be seen to have been considered .questionably These results indicate a considerable iiriproveu rancid 23 times during the .69.1day test, even after ment in stability .over the rlowfgiade yfat soap treatment with ortho-biphenylbiguanide. -I`t .was containing only the vamino-type vsoap 'antioxidant questionably rancid from the 17th day :to the Ai. Thestaioilityisof theorder of that obtained completion of .the test. 'It also had a high perf 5 with soap from bleached .prime tallow .contain`l oxide increase (33.8). 'l'he improved soaps made ing the soap antioxidant A4. It will also #bemoted Afrom .decolorized lowegrade fat in `,accordance from Table 1I that those soap samples treated with the Amethod .of `the .present invention (-1), in yaccordance with .the method of the present -.(2), 4and (3), will be seen to compare very fav.- irivention, i. e. samples (1)(3), showed 1.a ycori- Orably with the SOaD made from 'high-grade fat it) siderably` smaller increase in peroxide value Showing peroxide increases Of 20.2, 23.6, the .untlealed loxywgrglde and 28.1, respectively, as compared with the highgrade Vsoap increase of 24.3 A marked improvenient` is seen in the soaps containing fboth .the

-soap .and the phenolic antioxidant ,over `(the same i5' soaps containing only the phenolic antioxidant VSqgml .Slhlte VTS ddedt Wit? the* .50?? as Well as over the soapcontaining l,only the soap LOXlWr-l m 'U1 e epeumen s 1,0m Wmo? antioxidant as discussed above. With the phenolic data oi Tam-e5 I and n was Obtmefl' )Thls was' Aantioxidant alone, 'sam-ples (1), (-2), and (3') done, sme 1t 1S a general plafctl 1 1 htsap* became definitely rancidafter 48, 44, and 29 days. 20 makmg ingu-Ty 75 'SC-" employ Sodmm SI1-@afterespeciiveiy. With the combination of .the However, .m Order .t llustfat@ that the use Qf (Aj), the peroxide value obtained comparing favorably with that recorded kfor the soap prepared using high-erede bleached prime tallow..

phenolic antioxidant and the soap antioxidant, Sllh C-OmDOUIld iS D0@ GSSGIISJ 130 Che hlfBSErlt .these .samples Vere not rand at, the end of the method., the daftwof Table I Tl VJZtS I'ECO'CledShOlV.: ,69..day aging period ing the results of an accelerated aging test on Table vII Without Soap Antioxidant With Soap Antioxidant rTyne of Fat -Used in Soap Odor s ...y Odor w n Peroxide Peroxide v Increase Days Ltg .v Days, to, Increase Da' to Dsfo y('I) i (Good)y i C?) (7) (Good) (l) -Decolorized ltallow plus An...` 4 47 9 21.9 Y 4 9 6 0 54 20. 2 69 69 2g yDecolorzed tallow plus A; 2 49 9 25. 1 4 7 114 0 46 23.6 50 69 (3 Decolorized tallow p1 is Aa.. 7 A50 3 30. 3 1 2 8 15 l 44 28. 1 69 69 (4) `Decolorized tallow (No ph nolic antioxidant) i.V 3 l 57 K 0 36.6 0 l 25 1 v34 33. 8 v20 69 (5) Bleached prime tallow (no v antioxidant) -7 48 5 29. .6 l 0 l 1 0 59 24. 3 9 69 In the above table:

A1=2,5,ditertiarybutyl hydroquinone (0.1% by weight added).

, 2-6 di-tertiary-biityl p-cresol (0.1% by Weight added).

:tertiary-butyl phenol (0.1% byweight added).

- ortho-biphenyl biguanide. l

{(el- =This column represents number of timesvsample considered t0 be rancid dpr-ing (iQ-day aging period. A

(, A=This column representspnurnber of .times sample considered tube borderline ,case of rancidity during'the (iQ-day aging period.

' -**=Tlie`se columns 'give the approximate number of daysbefore the sample appeared to be definitely rancid or questionably rancid C?) may `he seen from the data in Table II, .SOPDIQPISCl from CSGOIOI'Zed 10W-grade tal- When .no antioxidant at all was used, soap made 10W Wlih and WlhOllt the .Cly Sle FYGSSHI from both the high-grade iat (5) and the low- Table IH grade fat (4) became rancid withinone day when A Y, aged at 50 C. and 100 per cent humidity. With Odor *a H only the ""hindered phenolic antioxidantl pre's- TypeigislgaagUsed Dayvsfo Days to ent, the soap made vfrom the lowfgrade iat be- C?) (H r (.1.) camequestionably rancid in from two to n,four l A days vand definitely rancid in seven to nine days. Dgfliorid ttfuow 01 15 14 29 l 0 l all The sample of soap prepared lOm 10W-grade fai? nlcoirzei taiiow 6 17 n l pus v.i i 5 o 20.6 29 29 .(4) `and tieated only with the amino type 502W Decloriged 110W antioxidant Ai or ortho-biphenyl bigiia-nide, begius 04%.@ and came questionably rancid in only twenty days '6%dry smeate 8 0 2&2 29 29 exposure to the conditions of this test, Whereas A f t 1 t1 In the above table: i

soap made irom high grade -a pius ie `soap (Aipiq-biplhenyi biguamde. b

is co umn represents num er o times sani le considered antioxidant Ai, was not even cruestionably rancid 6 t9 be mmm ming the may aging Peng@ p @t end of the A69-Clay teso. *HOWEVSYIQ when D t (1'f))=b1`ls1c oliimn refpreseiilts nxnber i tirns sample considered o e or er ine caseo ranci ity urin e29- a aging ciiod. the 10W-grade .fait Waits treated Wlth .a lm-.1' .**==llhesre oliiinns give the approxiginate numx'tger of dpays before dered phenohc antloxlqant, Samples (1).-(3) gcQ-g? @appeared to be definitely rancid or questionably and thereafter the soap .made from such fat The results of Table Ill were obtained by treated With ortlio-b1phenyl biguanide, the rea in t o l sultant product in the case of antioxidants Ai o g g a 50 C' and 100 per Cent hhmldlty and the orgaiioleptic determination or" iancidity was and As was not even questlonably ranld during carried out by a panel of three soap experts. as the 176511 pelld and that ret .A2 can be seen from the table, there is little effect qlleStOnably rancid Only after 50 dfYS :QXDQSDI'G attributable to the presence of the sodium sili-.

320 '12h52 iiclelild @eine @.Ondiiiiohs -Qf iihe test; 75 Gate, andvhence the method of the present invent. i

tion may be carried out either in the presence or absence of the silicate compound.

Similar tests to those recorded in Tables I and II were also conducted using ortho-tolyl bigu.

anide as the soap antioxidant. For example, a soap prepared in accordance with this invention from propane-decolorized low-grade tallow stabliZed with 0.1 per cent by weight p-tertiarybutyl phenol and containing 0.1 per cent by weight of the amino-type soap antioxidant, ortho-tolyl biguanide, proved very stable after 82 days of accelerated aging at both room temperature and at 50 C. Soap prepared from the same fat but without the presence of the synergistic antioxidant composition of the present invention, proved questionably rancid at 20 days and definitely rancid at 38 days accelerated aging at room temperature. When aged at 50 C. this soap was definitely rancid in 8 days.

One method of practicing the present invention will now be described in connection with the accompanying drawing which is adapted for the manufacture of kettle-boiled soap. It is to be understood, however, that the invention is not restricted to the specific apparatus and method described.

Referring to the drawing, a countercurrent decolorizing tower is designated as I0. Countercurrent decolorizing with liquefied, normally gaseous hydrocarbons, such as propane, ethane, or the like, has been described in the art and reference is made to U. S. Patents Nos. 2,118,454, 2,219,652, 2,367,671 and 2,383,535 for a detailed disclosure of variations of this operation. In the present method, any of the above decolorizing solvents may be used. Likewise, other known decolorizing methods may be applied.

For the purpose of illustration, the decolorizing solvent will be referred to as propane in the instant example. The solvent, propane, is fed into the decolorizing tower l through line Il. Low-grade fat, e. g. No. 2 tallow, in a liqueed state is fed into the top of the tower through line l2. Within the tower, the fat is passed in countercurrent relationship with the propane. The ratio of propane to fat is approximately 30 volumes to l. The temperature of the tower is maintained at about 180 F. and the pressure at about 550 p. s. i. The bottoms, i. e. color bodies and other impurities contained in the fatty material consisting of about per cent of the tallow, are drawn off through line I3 and discarded. The overhead product, i. e. decolorized tallow, is drawn from the tower through line I4 and 0.1 per cent of a hindered phenolic antioxidant is added continuously to this stream through line l5 from storage tank i6. The antioxidant may be added in any suitable manner, as for example a concentrated solution in some goodgrade fat such as white grease. The decolorized tallow containing the hindered phenolic antioxidant is then saponiiied in the usual manner known to the art. For example, 2,000 lbs. batch of the fat, stabilized with 0.1 per cent by weight of the hindered phenolic antioxidant, is added to a, soap-boiling kettle I1. Approximately 1,000 lbs. of water are then added through line I8 and the mixture heated and agitated by bubbling low pressure steam through it. When the mixture has reached its maximum temperature, about 100 C., 630 lbs. of a 45 per cent solution of sodium hydroxide isadded slowly through line I9 from storage 20 to the steamagitated mixture. This amount of caustic gives a siight excess (about 0.5 per cent) after the reaction is complete. The mixture is then boiled slowly for 2 or 3 hours. The product is tested for a slight excess of caustic after the reaction is complete, either by taste or with the use of an acid-base indicator. Sufficient sodium chloride is then added to grain the soap. The steam agitation is shut ori and a water layer, containing most of the excess sodium hydroxide, salt and the glycerin, settles to the bottom. This is drained through line 2l and about 1,000 lbs. of water added. The mixture is again brought to a boil and the graining operation is repeated. After the water layer is drained, the steam is turned on and allowed to bubble through the soap. This last boiling slowly dilutes any residual electrolyte until its concentration is such that phase separation will take place upon standing. The steam is then shut off and the soap is allowed to set at about C. overnight. It separates into two phases, a niger and a neat phase. The niger phase is on the bottom and is drawn off through line 2l to be added to future soap kettles. The neat soap is then drawn oii through line 22 and dried on a drum drier 23 at about 1GO-180 C'.

To 1,000 lbs. of this dried soap, suiiicient water is added from line 2d (approximately 8 10 per cent) so that a continuous sheet will be formed on the flaking mill. Then l lb. (0.1 per cent) of a soap antioxidant, e. g. ortho-biphenyl biguanide from tank 25, and 14.6 lbs. of 41 per cent N-brand sodium silicate (0.6 per cent dry basis) from tank 26 are mechanically mixed as in line 2i with the soap. This mixture is then thoroughly blended by several passes through the flaking mill 2S. On the last pass, the soap sheet is cut into ribbons, which after air-drying breaks into Flakes. These iiakes are then tested for rancidity in the manner described above.

In carrying out the present invention, it is contemplated that all fatty materials, including fatty acids obtained from low-grade fat sources, are to be included within the scope of the invention. The invention is also considered vto encompass the treatment of such material,

after decolorization by treatment with a decolorizing solvent or by bleaching with earth, carbon or the like, with any phenolic fat antioxidant followed by treatment of the soap made from such treated fatty material with any amino-type soap antioxidant, such as diphenyl-para-phenylene-diamine, cyanoguandine, the mercaptobenzothiazole salt of phenyl-biguanide, and ortho-biphenyl or ortho-tolyl biguanide.

Although the invention has been described in connection with the use of normally gaseous hydrocarbons such as propane for decolorizing the fatty materials, it is contemplated that in addition to the normally gaseous hydrocarbons, polar solvents such as acetone, methylethylketone, and normally liquid hydrocarbons such as butane or isobutane may be used as decolorizing solvents. In addition, fatty materials treated by carbon or earth bleaching methods or by any of the other known decolorizing methods are intended to be covered by the term decolorized fatty material.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

l. A method for the manufacture of stabiliz antioxidant; saponifying said fatty material containing said phenolic antioxidant to form a soap; and thereafter adding to tne soap thus formed a small amount of an amino-type soap antioxidant.

3. A method for the manufacture of stabilized soap from low-grade fatty materials which comprises: subjecting said low-grade fatty materials to treatment with a decolorizing solvent whereby two phases are formed, one phase containing color bodies and other impurities contained in said fatty material, and the other containing the decolorized fatty material; separating out the phase containing the decolorized fatty material, immediately adding to said decolorized fatty material a small amount of a phenolic fat antioxidant; saponifying said fatty material containing said phenolic antioxidant to form a soap; and thereafter adding to the soap thus formed a small amount of an amino-type soap antioxidant.

4. A method substantially as described in claim 3, wherein the deooloriz-ing solvent is a liquefied,

normally gaseous hydrocarbon.

5. A method for the manufacture of stabilized soap from low-grade, decolorized fatty materials comprising: incorporating in said fatty material immediately after decolorizing a small amount of a fat antioxidant; saponifying said fatty material containing said fat antioxidant; and adding to the soap thus formed a small amount of a soap antioxidant.

6. A method for the manufacture of stabilized soap from low-grade, decolorized fatty materials comprising: incorporating in said fatty material immediately after decoloriaing a small amount of a phenolic fat antioxidant; saponifying said fatty material containing said phenolic fat antioxidant; and adding to the soap thus formed a small amount of an amino-type soap antioxidant.

7. A method for the manufacture of stabilized soap from low-grade, decolorized fatty materials comprising: incorporating in said fatty material immediately after decolorization a small amount of a phenolic fat antioxidant, said phenolic antioxidant being relatively insoluble in dilute caustic; saponifying said fatty material containing said phenolic fat antioxidant; and adding to the soap thus formed a small amount of an aminotype soap antioxidant.

8. A method for the manufacture of stabilizedr soap from low-grade, decolorized fatty materials comprising: incorporating in said fatty material immediately after decolorization a small amount of a hindered phenolic fat antioxidant; saponifying said fatty material containing said phenolic fat antioxidant; and thereafter adding to the soap thus formed a small amount of a bguanide soap antioxidant.

9. A method substantially as described in claim 8 wherein the biguanide soap antioxidant'is ortho-biphenyl biguanide.

10. A method substantially as described in claim 8 wherein the biguanide soap antioxidant is ortho-tolyl biguanide.

11. A method for the manufacture of stabilized soap from low-grade, decolorized fatty materials comprising: incorporating in said fatty material immediately after decolorization a small amount of di-tertiary-butyl hydroquinone; saponifying said fatty material containing said 2,5 di-tertiary-butyl hydroquinone; and thereafter adding to the soap thus formed a small amount of an amino-type soap antioxidant.

12. A method for the manufacture of stabilized soap from low-grade, decolorized fatty materials comprising: incorporating in said fatty material immediately after decolorization a small amount of p-tertiary-butyl phenol; saponifying said fatty material containing said p-tertiarybutyl phenol; and after that adding to the soap thus formed a small amount of an amino-type soap antioxidant.

13. A method for the manufacture of stabilized soap from low-grade, decolorized fatty materials comprising; incorporating in said fatty material immediately after decolorization a small amount of 2-6 di-tertiary-butyl p-cresol; saponifying said fatty material containing said 2-6 di-tertiarybutyl p-cresol; and thereafter adding to the soap thus formed a small amount of an amino-type soap antioxidant.

14. A method for the manufacture of stabilized soap from low-grade, decoiorized fatty materials comprising: incorporating in said fatty material immediately after decolorization a small amount of 2,6, di-tertiary-butyl meta-cresci; saponifying said fatty material containing said 2,6, di-tertiary-butyl meta-cresol; and thereafter adding to the soap thus formed a small amount of an amino-type soap antioxidant.

15. A method for the manufacture of stabilized soap from low-grade, decolorized fatty materials comprising: incorporating in said fatty material immediately after decolorization a small amount of 2,4,6, tri-tertiary-butyl phenol; saponifying said fatty material containing said 2,4,6, tri-tertiary-butyl phenol; and thereafter adding to the soap thus formed a small amount of an aminotype soap antioxidant.

16. A stabilized soap comprising a mixture of the saponication product of low-grade, decolorized fatty materials containing a small amount of a fat antioxidant added immediately after decoloriaation and before saponiioation, and a small amount of a soap antioxidant.

17. A stabilized soap comprising a mixture of the saponication product of low-grade, decolorized fatty materials containing a small amount of phenolic fat antioxidant added immediately after decoiorization and before saponification, and a small amount of an amino-type soap antioxidant.

18. A stabilized soap comprising a mixture of the saponification product of low-grade, decolorized fatty materials containing a small amount of a hindered phenolic iat antioxidant added immediately after decolorization and before saponication and a small amount of a biguanide soap antioxidant.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,542,438 Divine June 16, 1925 1,820,744 Kaegebehn Aug. 25, `1931 2,029,506 Reed Feb. 4, 1936 2,221,333 Sibley Nov. 12, 1940 2,416,074 Weber Feb. 18, 1947 

1. A METHOD FOR THE MANUFACTURE OF STABLIZED SOAP FROM LOW-GRADE FATTY MATERIALS WHICH COMPRISED: DECOLORIZING SAID LOW-GRADE FATTY MATERIALS; IMMEDIATELY ADDING TO SAID DECOLORIZED FATTY MATERIAL A SMALL AMOUNT OF A FAT ANTIOXIDANT; SAPONIFYING SAID FATTY MATERIAL CONTAINING SAID ANTIOXIDANT TO FORM A SOAP; AND THEREAFTER ADDING TO THE SOAP THUS FROMED A SMALL AMOUNT OF A SOAP ANTIOXIDANT. 